Chain-End Functionalization with a Saccharide for 10 nm Microphase Separation: “Classical” PS-b-PMMA versus PS-b-PMMA-Saccharide

Abstract

Microphase-separated structures of block copolymers (BCPs) have attracted much attention as template materials for bottom-up nanofabrication. At the same time, chain-end modification has become a leading facile and efficient technique for fine-tuning the morphologies of microphase-separated structures generated from BCPs. Herein, we describe the preparation of well-defined polystyrene-block-poly­(methyl methacrylate)­s (PS-b-PMMAs) bearing highly hydrophilic mono/oligosaccharide moieties at their PMMA chain ends (SM-mono/oligosaccharides) as well as the impact of the mono/oligosaccharide on microphase separation behavior. PS-b-PMMAs were terminal-selectively transesterified using the titanium alkoxide of 6-azido-1-hexanol to introduce azido groups into the side chains of the terminal MMA units. The azido-functionalized PS-b-PMMAs were subsequently click reacted with ethynyl-functionalized mono/oligosaccharides to yield SM-mono/oligosaccharides. Small-angle X-ray scattering and microscopy experiments reveal that PS-b-PMMAs bearing maltotrioses at their chain ends (SM-MTs), and with total molecular weights of ∼10 kg mol–1, successfully form microphase-separated structures, although the unmodified PS-b-PMMAs exist in miscible states. Interestingly, the SM-MT with equivalent PS- and PMMA-MT-block volume fractions microphase separated to form a hexagonally close-packed cylinder with a domain spacing of 11.5 nm, rather than a lamellar structure, implying that the phase diagram for microphase separation is significantly affected by strong maltotriose aggregation. Hence, the results presented herein demonstrate that the incorporation of oligosaccharide moieties at chain ends is an efficient means of fine-tuning the size features as well as the morphologies of BCP microphase-separated structures.

Stable Thermotropic 3D and 2D Double Gyroid Nanostructures with Sub‐2‐nm Feature Size from Scalable Sugar–Polyolefin Conjugates

“…Further, while bulk thermotropic DG phases have been previously observed for glycolipids, [5, 13d] to the best of our knowledge, this same nanostructured morphology has not yet been reported for any class of saccharide‐hydrocarbon within an ultra‐thin film construct. Accordingly, a variable temperature synchrotron 2D GISAXS investigation of ultrathin films of 1 a that are supported on hydrophobic c‐Si substrates was conducted using various temperature ramp and jump profiles in order to determine if the unique stability observed in the bulk for the HPL and DG phases also occurs in ultrathin films.…”

Carbohydrates as Hard Segments for Sustainable Elastomers: Carbohydrates Direct the Self-Assembly and Mechanical Properties of Fully Bio-Based Block Copolymers

“…10,11 It should be noted here that previous studies by our group and Sita's group revealed that block copolymers (BCPs) consisting of hydrophobic polymers and oligosaccharides readily self-assembled into microphase-separated structures due to the strong segregation between the blocks, which was further enhanced by the rigid rod nature of the oligosaccharide. [12][13][14][15][16][17][18][19][20][21][22][23] We therefore envisioned that the integration of a rubbery hydrophobic polymer at the middle block and oligo/polysaccharide hard segments at the outer blocks could provide a novel bio-based elastomer, in which the microphase-separated carbohydrate hard domains act as a physical crosslink for the rubbery chains.…”

Maltotriose–Chlorin e6 Conjugate Linked via Tetraethyleneglycol as an Advanced Photosensitizer for Photodynamic Therapy. Synthesis and Antitumor Activities against Canine and Mouse Mammary Carcinoma Cells

“…The synthesis of Mal 3 –alkyne 1 has already been reported elsewhere. 35 The mixture of Mal 3 (500 mg, 991 μmol) and PA (900 μL, 14.1 mmol) was stirred at room temperature. The consumption of Mal 3 was monitored by TLC (silica gel 60 F 254 , CH 3 CN/H 2 O = 2:1).…”